(1) Field of the Invention
This invention relates to a high voltage generating apparatus for use in accelerating charged particles or the like, which generates a DC high voltage by rectifying and smoothing an AC voltage with diodes and capacitors.
(2) Description of the Prior Art
Known high voltage generating apparatus include the Cockcroft-Walton type, Schenkel type and insulating transformer type.
With the Cockcroft-Walton type and Schenkel type high voltage generating apparatus, a rectifier circuit must be formed with many diodes and capacitors connected in multiple stages. This entails an increase in ripples, and a deterioration in control characteristics due to a response delay in following load variations.
Conversely, if the number of stages of the diodes and capacitors in the rectifier circuit is reduced, the diodes and capacitors must work at a high voltage resistance. This results in the disadvantage of enlarging the entire apparatus since it requires large diodes and capacitors as well as a driver of high voltage output.
The above problems have led to development of high voltage generating apparatus of the insulating transformer type, one example of which is shown in FIG. 2.
This insulating transformer type high voltage generating apparatus comprises a driver 1, a primary coil 2 connected to the driver 1 and wound around an insulating magnetic core 3, a plurality of secondary coils 4 wound around the core 3, and rectifier circuits 5 connected to the secondary coils 4. The rectifier circuits 5 each including a diode and a capacitor have DC outputs connected in series to provide a DC high voltage.
According to this insulating transformer type high voltage generating apparatus, the diodes and capacitors constituting the rectifier circuits 5 may have a low voltage characteristic if the number of rectifier circuits is increased. Despite the increase in the number of rectifier circuits, the ripples can be lowered compared with a multi-stage Cockcroft-Walton type apparatus. Further, only a minor delay occurs in responding to load variations, and hence an excellent control characteristic is expected.
However, with the apparatus shown in FIG. 2, discharge may occur between the secondary coils 4 and surfaces of the insulating core 3, if a very high voltage through the insulating core 3 is used. Also the insulating material forming the core 3 may lose its insulation according to an internal discharge. Thus, there is a limit to the increase of voltage.